Preheat oven to 350 degrees. Spray a 9-inch square baking pan with cooking spray; line the bottom of pan with parchment paper.

Place apple slices in medium bowl and toss with 1 tablespoon sugar; set aside.

In large bowl sift together flour, baking soda, salt, cinnamon, nutmeg and allspice.

In another bowl cream together sugar and butter/margarine until smooth. Add vanilla; mix well. Add eggs, one at a time, to mixture; mix until smooth. Add chopped apples; mix with spatula to blend. Spoon flour-spice mixture into apple-sugar-butter mixture; mix well with spatula.

Place reserved apple slices on bottom of prepared pan; sprinkle with walnuts. Spoon batter over apples and walnuts; smooth batter with spoon. Bake 30 minutes or until firm in center; remove and cool on wire rack. Insert knife around edges to dislodge cake from pan; quickly turn pan upside down over serving plate. Slice with serrated knife to serve.